Field of the Disclosure
The present disclosure relates to the field of power electronics, and more particularly, to an LED driving circuit and method using a single inductor.
Description of the Related Art
LED lamps are widely used in the fields of lighting and decoration, as ideal products because they are energy-efficient and environment-friendly. Some specific driving circuits must be developed to achieve constant current control due to characteristics of the LED lamps. A driving circuit typically is an integrated chip 1, as shown in FIG. 1. The chip 1 is a constant current control chip for receiving a DC bus voltage and providing a constant current signal Vout1 through a BUCK converter including switches QM1, QR1 and an inductor L1. The constant current Vout1 is used for driving the LED lamps. When the LED light source includes a plurality of LED strings, a dimming controller (for example, MCU in FIG. 1) is used for regulating color temperature and brightness by dimming the plurality of LED strings. As shown in FIG. 1, a conventional dimming controller needs an additional power supply chip. Typically, the dimming controller has a relatively low supply voltage, for example, 3.3V or 5V. So a voltage obtained from the DC bus voltage cannot be directly used as the supply voltage for the dimming controller as it is usually larger than the supply voltage of the dimming controller. Thus, a voltage converter, such as a chip 2, is necessary for receiving the DC bus voltage, and generating a constant voltage signal Vout through a BUCK converter including switches QM2, QR2 and an inductor L2. The constant voltage signal Vout2 is used for dimming controller MCU.
As shown in FIG. 1, the conventional LED driving circuit has complex peripheral components, including at least two power transistors and at least two inductors. The number of chips is 2, which increases a product cost and introduces a complex control scheme.